(US4916323-A)      The optical circuit is formed by a first transistor, a first resistive element connected between control electrode and first output electrode of the first transistor. The first output electrode forms an emitter or source of the transistor, a second resistive element is connected between the control electrode and second output electrode of the first transistor. The second output electrode forms a collector or drain of the transistor and an array of photovoltaic elements is connected in parallel to the second resistive element.    A second transistor has a electrode connected to the second output electrode of the first transistor. High speed operation of the second transistor can be assured, any noise voltage applied to the control electrode of the second transistor can be effectively bypassed. The first transistor can be simultaneously formed in a substrate of the second transistor to be integralised therewith. (15pp)    (DE3832463-C)      The circuit comprises a first resistive element between a control electrode and a first transistor output electrode, the latter forming the emitter, or source, of the first transistor. Its collector, or drain is coupled to a second output electrode. A second resistive element is incorporated between the control electrode and the second output electrode.    To the second resistive element is in parallel a series-connection of photovoltaic elements. To the first transistor is coupled a second one, which is blocked when the first transistor is conductive. At the control electrode, the second transistor is coupled to the output electrode, forming the collector, or drain, of the first transistor. The first resistive element is of rectifier type.    ADVANTAGE -   Reliable mfr., due to formation of two transistors on common substrate.    (GB2210199-B)      A semiconductor device including a substrate of first and second conduction type semiconductor layers and forming an optical control circuit wherein a first resistive element is connected between a control electrode and a first output electrode of a first transistor, said first output electrode forming an emitter or source of the first transistor while its collector or drain is a second output electrode, a second resistive element is connected between the control electrode and the second output electrode of the first transistor, an array of photovoltaic elements is connected in parallel with the second resistive element and a second transistor is connected to the first transistor for being turned off when the first transistor is in conductive state, wherein said second transistor is connected at a control electrode thereof to said second output electrode forming said collector or drain of the first transistor, the second transistor comprises part of the first conduction type semiconductor layer formed on a surface of the second conduction type semiconductor layer, at least one of the first transistor and first and second resistive elements is formed on the same or different first conduction type semiconductor layer or layers and said first and second transistors being formed simultaneously in a common substrate.